光纤光栅波长干涉解调技术的研究

波长解调技术和装置是光纤光栅传感器的一个主要问题.因此,如何低成本高精度地将波长移动信号解调出来成为光纤光栅传感器实用化的关键技术之一.本文提出一种用2×2和3×3耦合器构成M-Z干涉仪作为光纤光栅的波长解调器,并对此进行了相关的理论分析和实验研究.实验结果与理论分析相符合.     

基于Sagnac的分布式光纤传感声学传感器

介绍了一种基于Sagnac的分布式光纤声学传感器. 这种声学传感器通过光电探测器、 数据采集卡、 滤波器和音频放大将3×3耦合器处干涉的光信号转换为电信号且实现音频信号的还原. 为了研究此分布式光纤声学传感器的性能, 分析了基于零频点实验声源扰动定位的原理, 并运用快速傅立叶变换将时域信号转化为频域信号显示声源扰动产生的零频点. 实验结果表明, 基于Sagnac的分布式光纤声学传感系统可以很好地实现声音信号的还原和定位.     

小信号幅度测量中的差分同步解调技术

本文介绍一种用于测量小信号幅度的电路，被测信号范围为微伏级到几毫伏。电路设计方法适用于将数模混合型正弦波发生器作为信号源的测量仪器。文中主要讨论两方面问题，对两个正弦波信号之差的正确解调和测量中的共模信号校正。     

Optimization of the frequency-modulated continuous wave technique for referencing and multiplexing intensity-based fiber optic sensors

In this paper, we demonstrate the interrogation of fiber optic intensity sensors by using the combination of the frequency-modulated continuous wave concept with the spectral selective reflectivity of fiber Bragg gratings. Thus, we multiplex these kinds of sensors with this technique having simultaneously a referenced system. The basis of this dual functionality is described and results are presented for the case of interrogation of two multiplexed intensity sensors. Their evaluation permits to establish the conditions to address a sensor network of this type. Also, it is proposed a strategy to implement this sensing approach without the requirement of using optical fiber delay lines in the sensor heads.     

基于光纤分布式传感器的时频定位技术

光纤单芯分布式传感系统可对传感线路上的扰动信号进行检测与定位,特别适合各种长距离的管道监控,如油管监控。传统的频域定位算法,依靠单独的几个频率点,有一定的局限性,并且如果扰动源未激发出所需要的频率范围,就无法获得频率缺失点,这种判断方法就会失效。提出了一种简单的时域定位算法,与频域算法进行互补,提高了系统的稳定性和普适性。     

便携式光纤Bragg光栅波长解调仪的研制

近年来光纤光栅在传感领域中的应用研究日益得到关注，其中光纤光栅波长解调是光纤光栅传感器得到应用推广的关键之一。针对大型建筑结构监测应用领域，研制了一种便携式光纤Bragg光栅波长解调仪。解调仪基于无源比例解调原理，以熔融拉锥器件作为线性滤波器，采用锁相放大技术提取微弱信号，并利用单片机控制光纤Bragg光栅波长信息的采集、显示以及存储。解调仪结构简单、成本低，可实现大量程波长测量。实验表明，该光纤光栅解调仪解调范围达15nm，波长测量精度为12．4pm。     

A fiber loop mirror temperature sensor demodulation technique using a long-period grating in a photonic crystal fiber and a band-pass filter

A fiber loop mirror (FLM) temperature sensor using a long-period grating (LPG) written in a photonic crystal fiber (PCF) and a band-pass filter as a demodulator is proposed. By utilizing the stable filtering function of the LPG in the PCF, the resonant wavelength variation of the FLM with temperature is transferred effectively to the intensity variation of the output light. By monitoring the light intensity of the band-pass of the filter, temperature applied on the FLM is deduced by an optical power meter. Experiment results show that the temperature sensitivity is high as ~1.742 dB/ °C when a filter with a full width at half maximum 3 nm and the center at 1545 nm is used.     

光纤接口同轴精密加工

陶瓷光纤接口要求外圆与内孔的同轴度１μｍ、圆度５μｍ,加工精度达微米级和亚微米级。本文对光纤接口精密同轴加工方法进行介绍,并就光纤接口数控同轴磨床作一些简介。     

基于USB2·0的高速光纤光栅解调系统的研制

研制一种基于USB2.0通信的高速光纤Bragg光栅解调仪。采用EZ-USBFX2系列的CY7C68013芯片为核心作为USB外围设备,设计并实现光纤光栅传感的数据采集与USB2.0的高速数据传输系统。解调仪波长解调范围为1542~1551nm,检测精度为15pm,数据刷新速度为200kHz,而目前同等成本的解调仪速度仅为几百赫兹。     

Novel fiber optic sensor for ice type detection

This paper reports on a novel fiber-optic ice sensor featuring oblique fiber end-faces, not perpendicular to the fiber axis. The inclination angles of the end-faces were respectively 50° and 30° for the source and signal fiber bundles. Ice-growth curves obtained in an icing wind tunnel showed that with increasing ice thickness, the output voltage of this sensor would reduce rapidly for glazed ice, increase rapidly for rime ice, and make no remarkable change for mixed ice. This significant difference is caused by the different optical intensity distributions for different ice types and can be used to accurately identify the ice type for aerospace applications.     

光纤陀螺仪自动测试系统设计

为了满足多种型号光纤陀螺仪的复杂测试需求,该文设计了一种光纤陀螺仪自动测试系统。该测试系统具有基于FPGA的硬件主板与模块化可更换的陀螺仪电源、信号采集子板,支持多串口测试协议,采集的数据通过串口转换后统一发送到上位机软件端进行存储、分析和显示,可导入模板实现测试、参数标定全程自动化,并生成统计报表。该系统遵循GJB 2426A—2004标准,能兼容市面90%以上的各型光纤陀螺仪,可自动化完成光纤陀螺仪的基本性能测试,大大提升产品研发检测的效率。     

光纤陀螺用SLD光源的控制方法研究

光源控制技术是光纤陀螺技术研究领域的关键技术之一.为进一步提高光源的控制精度,从SLD光源驱动原理出发,提出光源模拟控制与数字控制方案,分析了电路原理,结合实际研究情况,从恒流精度、温控精度及光功率等关键技术指标出发,对两种方案进行比较并给出结论.     

Implementation of an open-loop control technique for high-speed micropositioning in a single-point diamond turning process

An investigation is undertaken to minimize residual vibrations associated with high-speed, low-amplitude machining processes. A numerically computed input signal allows the system to follow a desired output trajectory once an accurate dynamic model of the system is developed. Specific application of this method is focused on controlling tool motion while cutting micron depth surface features into a flat, rotating workpiece during a single-point diamond turning process. The synthesized input signal, applied open-loop, is used to eliminate transient surface features that are created by uncontrolled motion of the tool when it is plunged into the workpiece surface during the cutting process. Controlled and uncontrolled cuts are shown to demonstrate a significant improvement in resulting surface features.     

Digitalization optical open loop test system for fiber optic gyroscope

In order to receive and process the open loop signal from fiber optic gyroscopes speedily, stably and expediently, and to realize the amity interface between human and machine, a digital system that can convert GPIB (general purpose interface bus) parallel bus into Universal Serial Bus is developed. All the interface functions of GPIB and the hardware system are realized through FPGA. With a digital sampling and processing system designed with VC++ in Windows platform, the real-time controlling procedure, high-speed receiving and sending data can be carried out, and the results can be displayed too. So the design of the system is flexible, the reliability and the stability are improved, error rate is no more than 10⁻¹¹, the highest bit rate is 8 MB/s and the open loop detection system for optic fiber gyros achieves standardization and complete digitalization simultaneously. __________ Translated from Chinese Journal of Scientific Instrument, 2005, 26(10) (in Chinese)     

EMD- and LWT-based stochastic noise eliminating method for fiber optic gyro

Stochastic noise in a fiber optic gyro (FOG) is mainly caused by white noise and 1/f^γ fractal noise. The latter noise is characterized by long-term correlation, self-similarity and spectral density with 1/f^γ power law. The application of the empirical mode decomposition (EMD) method and the lifting wavelet transform (LWT) as a novel EMD–LWT technique has been proposed and implemented in denoising the stochastic noise generated for a FOG. The EMD method is a novel nonlinear and non-stationary signal processing method and the LWT is a lifting scheme of wavelet transform. Experimental results of the FOG data have validated the feasibility of the proposed method, which is more effective than the denoising methods that use either LWT or the EMD method.     

极坐标下LAMOST光纤坐标检测方案

介绍极坐标下用多个线阵CCD对大尺度范围内多目标位置检测方法及系统搭建情况.对LAMOST光纤定位系统中球面焦面板上4000个光纤头位置的检测,采用极坐标旋转扫描装置进行检测.试验系统主要包括:控制主机,多个线阵CCD,精密旋转台,扫描梁,旋转平台,积分球光源以及自行设计的数据处理程序.检测装置包括精密旋转台和扫描梁,后者由多片线阵CCD软拼接而成,采用"光重心法"对光纤出射光斑处理从而获取光纤端部的位置.实验结果理想.     

数字闭环干涉式光纤陀螺的控制器设计与仿真

光纤陀螺与传统的机械陀螺相比,具有动态范围大、成本低、体积小、可靠性高等优点.数字闭环干涉式光纤陀螺(IFOG)的动态性能受控制系统设计的影响.现根据光纤陀螺数字闭环检测过程,建立了控制系统的数学模型,设计了模糊自适应PID控制器.仿真结果显示,设计的控制器能够有效地增强系统的鲁棒性,缩短调节时间,改善系统的动态性能.     

A comparison of light spot hydrophone and fiber optic probe hydrophone for lithotripter field characterization

The performance of a newly developed light spot hydrophone (LSHD) in lithotripter field characterization was compared to that of the fiber optic probe hydrophone (FOPH). Pressure waveforms produced by a stable electromagnetic shock wave source were measured by the LSHD and FOPH under identical experimental conditions. In the low energy regime, focus and field acoustic parameters matched well between the two hydrophones. At clinically relevant high energy settings for shock wave lithotripsy, the measured leading compressive pressure waveforms matched closely with each other. However, the LSHD recorded slightly larger |P_| (p < 0.05) and secondary peak compressive pressures (p < 0.01) than the FOPH, leading to about 20% increase in total acoustic pulse energy calculated in a 6 mm radius around the focus (p = 0.06). Tensile pulse durations deviated ~5% (p < 0.01) due to tensile wave shortening from cavitation activity using the LSHD. Intermittent compression spikes and laser light reflection artifacts have been correlated to bubble activity based on simultaneous high-speed imaging analysis. Altogether, both hydrophones are adequate for lithotripter field characterization as specified by the international standard IEC 61846.     

Absolute calibration method for nanosecond-resolved, time-streaked, fiber optic light collection, spectroscopy systems

This paper describes a convenient and accurate method to calibrate fast (<1 ns resolution) streaked, fiber optic light collection, spectroscopy systems. Such systems are inherently difficult to calibrate due to the lack of sufficiently intense, calibrated light sources. Such a system is used to collect spectral data on plasmas generated in electron beam diodes fielded on the RITS-6 accelerator (8-12MV, 140-200kA) at Sandia National Laboratories. On RITS, plasma light is collected through a small diameter (200 μm) optical fiber and recorded on a fast streak camera at the output of a 1 meter Czerny-Turner monochromator. For this paper, a 300 W xenon short arc lamp (Oriel Model 6258) was used as the calibration source. Since the radiance of the xenon arc varies from cathode to anode, just the area around the tip of the cathode ("hotspot") was imaged onto the fiber, to produce the highest intensity output. To compensate for chromatic aberrations, the signal was optimized at each wavelength measured. Output power was measured using 10 nm bandpass interference filters and a calibrated photodetector. These measurements give power at discrete wavelengths across the spectrum, and when linearly interpolated, provide a calibration curve for the lamp. The shape of the spectrum is determined by the collective response of the optics, monochromator, and streak tube across the spectral region of interest. The ratio of the spectral curve to the measured bandpass filter curve at each wavelength produces a correction factor (Q) curve. This curve is then applied to the experimental data and the resultant spectra are given in absolute intensity units (photons∕sec∕cm(2)∕steradian∕nm). Error analysis shows this method to be accurate to within +∕- 20%, which represents a high level of accuracy for this type of measurement.     

强度调制光纤位姿传感器的检测性能提高技术

本文研究了强度调制光纤传感器的反射信号检测技术,提出基于自扫描光电二极管阵列(SSPA)取样积分的时域光强检测方法,它具有信号处理简单,有效抑制环境光和电路背景噪声影响的特点,该方法的实施有效地提高了强度调制传感器的测量精度和稳定性.